Grease composition and rolling bearing

ABSTRACT

The present invention is a grease composition, comprising a fluorine-based grease, a urea-based grease and a soap-based grease (a calcium complex soap thickener, a calcium soap thickener, a barium soap thickener, a magnesium soap thickener or a sodium soap thickener), and a rolling bearing in which the grease composition is filled.

This is a continuation of International Application No.PCT/JP2017/043140 filed on Nov. 30, 2017, and claims priority fromJapanese Patent Application JP2016-233443 filed on Nov. 30, 2016, andJapanese Patent Application JP2017-220393 filed on Nov. 15, 2017, thedisclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a grease composition and a rollingbearing, and particularly to a grease composition realizing excellentacoustic characteristics not only under a high temperature and highspeed environment but also under a high load environment, and a rollingbearing suitable for a small motor.

BACKGROUND ART

As a rolling bearing used for small motors such as a fan motor and ahigh speed motor used for automobiles, there is for example, so-calledsmall diameter ball bearing having an outer diameter of 22 mm or less.Since such a small diameter ball bearing is required to have durabilityunder a high temperature environment, a fluorine-based grease excellentin heat resistance and oxidation resistance, a hybrid grease of afluorine-based grease and a urea-based grease excellent in heatresistance, and the like are conventionally used as lubricants.

For example, Patent Document 1 discloses a rolling bearing filled with agrease containing fluororesin particles as a thickener, a specificaspartic acid ester-based rust inhibitor and an oiliness agent in afluorine-based base oil (perfluoropolyether oil), in order to realizehigh temperature durability and low temperature torque property.

In addition, a grease composition containing a perfluoropolyether baseoil and a specific carboxylic acid metal salt as a thickener isproposed, which can improve wear resistance with respect to counterpartmaterials, leakage resistance, washability and the like while taking thecost into consideration (Patent Document 2).

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: Japanese Patent No. 4239514-   Patent Document 2: Japanese Patent No. 4505954

SUMMARY OF INVENTION Problems to be Solved by Invention

Although the above fluorine-based grease, particularly a fluorine-basedgrease using perfluoropolyether as a base oil, is excellent in heatresistance, it is known that when the fluorine-based grease is usedunder a high load or an overload condition due to mis-assembly, thefluorine oil (perfluoropolyether) which is a base oil decomposes togenerate hydrofluoric acid, whereby corrosion on a metal surface such asa raceway surface of the bearing is caused. The metal corrosion on theraceway surface may become a cause of deterioration of acousticcharacteristic and occurrence of rotation failure.

Therefore, there is a demand for a grease capable of preventing rotationfailure and noise increase in rolling bearings not only under a hightemperature and high speed condition but also under a high loadcondition.

The present disclosure has been conceived in view of such a situation,and an object of the present disclosure is to provide a greasecomposition capable of preventing noise increase under high temperatureand high speed condition as well as under a high load condition, andalso a rolling bearing excellent in heat-resistant acousticcharacteristic and load-bearing acoustic characteristic by applying thegrease composition of the present disclosure.

Means for Solving the Problem

The inventors of the present application have conducted intensivestudies to achieve the above object and, as a result, found that byblending in base oil specific amounts of three types of thickeners,i.e., a fluorine-based thickener, a urea-based thickener and asoap-based thickener such as a calcium complex soap thickener, a greasecomposition excellent in heat resistance and load resistance and capableof preventing noise increase in a high temperature and high speed testand a high load test can be obtained.

That is, one aspect according to the present disclosure relates to agrease composition, containing a fluorine-based base oil and anon-fluorine-based base oil as base oils; and a fluorine-basedthickener, a urea-based thickener and at least one soap-based thickenerselected from the group consisting of a calcium complex soap thickener,a calcium soap thickener, a barium soap thickener, a magnesium soapthickener and a sodium soap thickener as thickeners.

As a preferred embodiment according to the present disclosure, it ispreferable that the urea-based thickener contains at least one of analiphatic-aromatic urea, an alicyclic-aliphatic urea and an aliphaticurea.

It is preferable that the urea-based thickener contains a diureacompound represented by the following General Formula (1):

R₁—NHCONH—R₂—NHCONH—R₃  (1)

(in the formula, R₁ and R₃ each independently represent a monovalentaliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group ora monovalent aromatic hydrocarbon group, and at least one of R₁ and R₃represents a monovalent aliphatic hydrocarbon group or a monovalentalicyclic hydrocarbon group, and

R₂ represents a divalent aromatic hydrocarbon group).

It is preferable that the grease composition contains 70 mass % to 90mass % of a total amount of the fluorine-based base oil and thenon-fluorine-based base oil, 9 mass % to 18 mass % of the fluorine-basedthickener, 0.5 mass % to 7 mass % of the urea-based thickener, and 0.3mass % to 3 mass % of the calcium complex soap thickener, based on atotal amount (100 mass %) of the grease composition. It is furtherpreferable that the calcium complex soap thickener is a calcium complexsoap of an aliphatic dicarboxylic acid and a monoamide monocarboxylicacid.

Alternatively, it is preferable that the grease composition contains 70mass % to 90 mass % of a total amount of the fluorine-based base oil andthe non-fluorine-based base oil, 9 mass % to 18 mass % of thefluorine-based thickener, 0.5 mass % to 7 mass % of the urea-basedthickener, and 0.3 mass % to 3 mass % of the calcium soap thickener,based on a total amount of the grease composition.

Alternatively, it is preferable that the grease composition contains 70mass % to 90 mass % of a total amount of the fluorine-based base oil andthe non-fluorine-based base oil, 9 mass % to 18 mass % of thefluorine-based thickener, 0.5 mass % to 7 mass % of the urea-basedthickener, and 0.6 mass % to 3.6 mass % of the barium soap thickener,based on a total amount of the grease composition.

Alternatively, it is preferable that the grease composition contains 70mass % to 90 mass % of a total amount of the fluorine-based base oil andthe non-fluorine-based base oil, 9 mass % to 18 mass % of thefluorine-based thickener, 0.5 mass % to 7 mass % of the urea-basedthickener, and 0.6 mass % to 3.6 mass % of the magnesium soap thickener,based on a total amount of the grease composition.

Alternatively, it is preferable that the grease composition contains 70mass % to 90 mass % of a total amount of the fluorine-based base oil andthe non-fluorine-based base oil, 9 mass % to 18 mass % of thefluorine-based thickener, 0.5 mass % to 7 mass % of the urea-basedthickener, and 0.6 mass % to 3.6 mass % of the sodium soap thickener,based on a total amount of the grease composition.

It is preferable that the non-fluorine-based base oil is one or moreselected from the group consisting of a hydrocarbon-based synthetic oil,an ether-based synthetic oil, an ester-based synthetic oil, and asilicone-based synthetic oil.

The present disclosure also relates to a rolling bearing in which thegrease composition is filled.

Effect of the Invention

According to the present disclosure, it is possible to provide a rollingbearing having a good acoustic performance under a high temperature anda high load and excellent in heat resistance and load resistance byapplying the grease composition having the above constitution to arolling bearing.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view for explaining a structure of a rollingbearing according to the present disclosure.

FIG. 2 is a graph showing results (Anderon values of M band) of a heatresistance test and a load resistance test by an Anderon meter when thecontent of calcium complex soap thickener is changed in a mixed greaseof three types of greases, i.e., a fluorine-based grease, a urea-basedgrease and a calcium complex soap grease.

FIG. 3 is a graph showing results (Anderon values of M band) of the heatresistance test and load resistance test by the Anderon meter when thecontent of calcium soap thickener is changed in a mixed grease of threetypes of greases, i.e., a fluorine-based grease, a urea-based grease anda calcium soap grease.

FIG. 4 is a graph showing results (Anderon values of M band) of the heatresistance test and load resistance test by the Anderon meter when thecontent of barium soap thickener is changed in a mixed grease of threetypes of greases, i.e., a fluorine-based grease, a urea-based grease anda barium soap grease.

FIG. 5 is a graph showing results (Anderon values of M band) of the heatresistance test and load resistance test by the Anderon meter when thecontent of magnesium soap thickener is changed in a mixed grease ofthree types of greases, i.e., a fluorine-based grease, a urea-basedgrease and a magnesium soap grease.

FIG. 6 is a graph showing results (Anderon values of M band) of the heatresistance test and load resistance test by the Anderon meter when thecontent of sodium soap thickener is changed in a mixed grease of threetypes of greases, i.e., a fluorine-based grease, a urea-based grease anda sodium soap grease.

FIG. 7 is a graph showing results (Anderon values of M band) of the heatresistance test and load resistance test by the Anderon meter when thecontent of lithium soap thickener is changed in a mixed grease of threetypes of greases, i.e., a fluorine-based grease, a urea-based grease anda lithium soap grease.

DESCRIPTION OF EMBODIMENTS

As described above, the fluorine-based grease has a problem thatfluorine oils (base oils) decompose during use under a high load andcorrosion of the metal surface occurs due to generation of hydrofluoricacid, and among the fluorine oils, this problem particularly easilyoccurs in a grease using perfluoropolyether having a straight chainstructure as a base oil.

In order to solve this problem, the inventors of the present applicationhave investigated a preferred constitution of a grease compositionhaving heat resistance and load resistance, and it is found thatblending a hybrid grease of a fluorine-based grease and a urea-basedgrease which has good heat resistance, with a soap-based greasecontaining a soap-based thickener such as a calcium complex soapthickener, as a thickener, can lead to solution against corrosion on theraceway surface in a high load condition.

Then, the inventors of the present application first compared andexamined the influence of the changes in the blending amounts of theurea-based grease and the calcium complex soap grease on the heatresistance and load resistance of a mixed grease by changing theirblending amounts while maintaining constant the blending amount of thefluorine-based grease to eliminate the influence of the fluorine-basedgrease in the mixed grease of the three types of greases (thefluorine-based grease, the urea-based grease, and the calcium complexsoap grease as an example of the soap-based grease). In the presentdisclosure, a bearing using the mixed grease was rotated under a hightemperature and high speed condition or a high load condition, then theacoustic performance was measured using an Anderon meter, and theobtained Anderon value was used as an indicator of heat resistance andload resistance. Therefore, as described later, in the presentdisclosure, a load resistance test (load resistance evaluation) means anacoustic evaluation test after rotating the bearing under a high loadcondition, and a heat resistance test (heat resistance evaluation) meansan acoustic evaluation test after rotating the bearing under a hightemperature environment.

Surprisingly, when the content of the calcium complex soap thickener waslarger than a specific amount, it was confirmed that, in the loadresistance test, the noise increase evaluated by the Anderon value canbe prevented, and the acoustic evaluation becomes better as the contentincreases.

On the other hand, in the heat resistance test, the noise increase wasprevented until the content of the calcium complex soap thickenerreached a specific amount, but the noise increase occurred once thespecific amount was exceeded.

Based on these findings, the similar evaluation was performed also fordifferent blending amount of the fluorine-based grease, and the blendingamount for obtaining good acoustic characteristic was confirmed in boththe load resistance test and the heat resistance test.

Further, the similar evaluation was performed by using a calcium soapgrease, a barium soap grease, a magnesium soap grease and a sodium soapgrease as soap-based greases, and in these soap-based greases, ablending amount capable of obtaining good acoustic characteristics wasalso confirmed in both the load resistance test and the heat resistancetest.

As one example, FIG. 2 shows results obtained by an Anderon meter in aheat resistance test (preload: 39 N, test temperature: 180° C., rotationspeed: 21,000 rpm, 200 hours) and in a load resistance test (preload:500 N, test temperature: room temperature, rotation speed: 3,000 rpm,100 hours) when the blending amounts of the fluorine-based grease, theurea-based grease and the calcium complex soap grease are changed in amixed grease (grease composition) of three types of grease (thefluorine-based grease, the urea-based grease and the calcium complexsoap grease). Detailed procedures and details of the results are givenin Examples described below.

In detail, FIG. 2 shows the content (mass %) of the calcium complex soapthickener based on the total amount of the mixed grease indicated by thehorizontal axis, and the Anderon value of M band after each testindicated by the vertical axis, when in mixed greases of three types ofgrease, the blending amount of the fluorine-based grease is changed from90 mass % to 49 mass % (the content of the fluorine-based thickenerbeing in the range of 17.8 mass % to 9.8 mass % based on 100 mass % ofthe mixed grease), the blending amount of the urea-based grease ischanged from 0 mass % to 48 mass % (the content of the urea-basedthickener being in the range of 0 mass % to 7.2 mass % based on 100 mass% of the mixed grease), and the blending amount of the calcium complexsoap grease is changed from 0 mass % to 29 mass % (the content of thecalcium complex soap thickener being in the range of 0 mass % to 4.3mass % based on 100 mass % of the mixed grease), and the Anderon valuesfor each grease is measured after the heat resistance test or after theload resistance test. In FIG. 2, the broken line parallel to thehorizontal axis indicates the Anderon value of 15. In the testconditions of the Examples, significant wear was observed when theAnderon value was 15 or more. Therefore, it was evaluated that theAnderon value less than 15 is preferable.

As shown in FIG. 2, when the content of the calcium complex soapthickener is more than a specific amount (in the case of FIG. 2, about0.3 mass %, more particularly 0.5 mass %), it is verified that, in theload resistance test (high load test: ▪ (black square)), the noiseincrease evaluated by the Anderon value is prevented, and the acousticevaluation becomes better as the content increases.

On the other hand, in the heat resistance test (high temperature andhigh speed test: ⋄ (diamond)), although the prevention of noise increaseis achieved until the content of the calcium complex soap thickenerreaches a specific amount (about 3 mass % in the case of FIG. 2), thenoise increase occurs once the specific amount is exceeded.

As shown in the results of FIG. 2, it can be confirmed that when thecontent of the calcium complex soap thickener based on the total amountof the mixed grease is in the range of 0.3 mass % to 3 mass %,particularly 0.5 mass % to 3 mass % (the blending amount of the calciumcomplex soap grease based on the total amount of the mixed grease beingin the range of 2 mass % to 20 mass %, particularly 4 mass % to 20 mass%) in the mixed grease of three types of greases, i.e., thefluorine-based grease, the urea-based grease and the calcium complexsoap grease, good acoustic characteristic can be obtained in both theload resistance test and the heat resistance test. In FIG. 2, the rangeindicated by the arrow parallel to the horizontal axis indicates thecontent range of the calcium complex soap thickener which can providegood acoustic characteristic (Anderon value: less than 15) in both theload resistance test and the heat resistance test.

Based on the results shown in FIG. 2, the inventors have investigatedthe suitable upper and lower limits of the blending proportion of thesethree types of greases (three types of thickeners) to accomplish theinvention according to the present disclosure.

A grease composition to be filled in a rolling bearing according to thepresent disclosure (hereinafter simply referred to as “greasecomposition”) is characterized by combining specific thickeners asdescribed below in detail.

[Rolling Bearing]

First, preferred embodiments of a rolling bearing according to thepresent disclosure will be described in detail with reference to theaccompanying drawings. The invention according to the present disclosureis not limited by the following embodiments.

FIG. 1 is a cross-sectional view of a rolling bearing (ball bearing) 10according to a preferred embodiment of the present disclosure.

The rolling bearing 10 has a basic structure similar to that of theconventional rolling bearing and includes an annular inner ring 11, anannular outer ring 12, a plurality of rolling elements 13, a cage 14,and annular sealing members 15 (15 a, 15 b). The inner ring 11 is acylindrical structure to be disposed coaxially with a central axis of ashaft.

The outer ring 12 is a cylindrical structure disposed coaxially with theinner ring 11 on an outer circumferential side of the inner ring 11.

Each of the plurality of rolling elements 13 is a sphere (ball) disposedon a raceway in a bearing space (annular space) 16 formed between theinner ring 11 and the outer ring 12. That is, the rolling bearing 10 inthe present embodiment is a ball bearing.

In the bearing space 16, a grease composition G is filled as alubricant. The annular sealing members 15 (15 a, 15 b) are formed of,for example, a steel plate extending from an inner circumferentialsurface of the outer ring 12 toward the inner ring 11 side, and seal thebearing space 16 from the outside. The amount of the grease compositionG filled in the bearing space 16 is, for example, 5% to 50% of thevolume of the bearing space 16. An amount of about 25% to 35% ispreferred in order to achieve both the torque performance and the lifeperformance.

On the inner circumferential surface of the outer ring 12, a raceway 12a being a concave portion having an arc-shaped cross section is formedin a circumferential direction of the outer ring 12. In addition, on anouter peripheral surface of the inner ring 11, a raceway 11 a being aconcave portion having an arc-shaped section is formed in acircumferential direction of the inner ring 11. The plurality of rollingelements 13 are guided in the circumferential direction by the raceway11 a and the raceway 12 a.

The cage 14 is disposed in the track and is configured to retain theplurality of rolling elements 13. The cage 14 is an annular memberinstalled coaxially with the central axis of the shaft, and includes aplurality of concave portions (ball pockets) for retaining the rollingelements 13 around the central axis. The shape (such as crown shape orribbon type) and the material (such as steel plate or resin) of the cage14 can be selected appropriately and are not limited to specific shapesand materials. In the rolling bearing 10 having the above configuration,the grease composition G acts to reduce the friction between the rollingelements 13 and the cage 14 and the friction between the rollingelements 13 and the inner ring 11 or the outer ring 12. As can be seenfrom the configuration shown in FIG. 1, the grease composition G filledin the rolling bearing 10 enters between the rolling element 13 and theinner ring 11 or the outer ring 12 when the rolling bearing 10 rotates.

[Grease Composition]

Next, the grease composition to be filled in the rolling bearing of thepresent disclosure will be described.

<Base Oil>

In the grease composition to be filled in the rolling bearing accordingto the present embodiment, a fluorine-based base oil and anon-fluorine-based base oil are used as base oils.

Examples of the fluorine-based base oil include those containingperfluoropolyether (PFPE) as a main component. PFPE is a compoundrepresented by the general formula:RfO(CF₂O)_(p)(C₂F₄O)_(q)(C₃F₆O)_(r)Rf (Rf: perfluoro lower alkyl group;p, q, and r: integer).

Perfluoropolyether is broadly classified into a linearperfluoropolyether and a side-chain perfluoropolyether, and the linearperfluoropolyether has a smaller temperature dependency of kineticviscosity than the side-chain perfluoropolyether. This means that thelinear perfluoropolyether has a lower viscosity than the side-chainperfluoropolyether in a low temperature environment and has a higherviscosity than the side-chain perfluoropolyether in a high temperatureenvironment. In particular, when it is assumed to be used in a hightemperature environment, from the viewpoint of preventing the leakage ofthe grease from the applied portion and resulting lack of the grease, itis desirable that the viscosity in a high temperature environment behigh, that is, it is preferable to use a linear perfluoropolyether.

The non-fluorine-based base oil is not particularly limited, andhydrocarbon-based synthetic oils, ether-based synthetic oils such asalkyl ether oils and alkyl diphenyl ether oils, ester-based syntheticoils, and silicone-based synthetic oils, which are generally used as agrease base oil, can be used alone or in combination as thenon-fluorine-based base oil.

Examples of the hydrocarbon-based synthetic oils includepolyalphaolefins (PAO) such as normal paraffin, isoparaffin, polybutene,polyisobutylene, a 1-decene oligomer, a 1-decenethylene oligomer or thelike.

Examples of the ester-based synthetic oils include: diester oils such asdibutyl sebacate, di-2-ethylhexyl sebacate, dioctyl sebacate, dioctyladipate, diisodecyl adipate, ditridecyl adipate, ditridecyl phthalate,and methyl acetylcinolate; aromatic ester oils such as trioctyltrimellitate, tri-2-ethylhexyl trimellitate, tridecyl trimellitate,tetraoctyl pyromellitate and tetra-2-ethylhexyl pyromellitate; polyolester oils such as trimethylolpropane caprylate, trimethylolpropanepelargonate, pentaerythritol-2-ethylhexanoate and pentaerythritolpelargonate; and carbonate ester oils.

Examples of the alkyl diphenyl ether oils include monoalkyl diphenyl,dialkyl diphenyl, polyalkyl diphenyl, or the like.

Among the above, the aromatic ester oils are preferred, and can be usedalone or in combination.

The blending proportion of the fluorine-based base oil and thenon-fluorine-based base oil is not particularly limited, and forexample, the ratio (fluorine-based base oil: non-fluorine-based baseoil) based on the total amount (100 mass %) of the base oils can be (95mass % to 5 mass %: 5 mass % to 95 mass %), or more preferably, (95 mass% to 40 mass %: 5 mass % to 60 mass %),

In addition, the total amount of the fluorine-based base oil and thenon-fluorine-based base oil in the total amount of the greasecomposition according to the present disclosure can be 70 mass % to 90mass %, preferably 75 mass % to 95 mass % and more preferably 75 mass %to 85 mass %.

<Thickener>

A fluorine-based thickener, a urea-based thickener and at least onesoap-based thickener selected from the group consisting of a calciumcomplex soap thickener, a calcium soap thickener, a barium soapthickener, a magnesium soap thickener and a sodium soap thickener areadded as thickeners to the grease composition according to an embodimentof the present invention.

Among these, it is preferable to contain 9 mass % to 18 mass % of thefluorine-based thickener, 0.5 mass % to 7 mass % of the urea-basedthickener, and 0.3 mass % to 3 mass % of the calcium complex soapthickener, based on the total amount of the grease composition.

Alternatively, it is preferable to contain 9 mass % to 18 mass % of thefluorine-based thickener, 0.5 mass % to 7 mass % of the urea-basedthickener, and 0.3 mass % to 3 mass % of the calcium soap thickener,based on the total amount of the grease composition.

Alternatively, it is preferable to contain 9 mass % to 18 mass % of thefluorine-based thickener, 0.5 mass % to 7 mass % of the urea-basedthickener, and 0.6 mass % to 3.6 mass % of the barium soap thickener,based on the total amount of the grease composition.

Alternatively, it is preferable to contain 9 mass % to 18 mass % of thefluorine-based thickener, 0.5 mass % to 7 mass % of the urea-basedthickener, and 0.6 mass % to 3.6 mass % of the magnesium soap thickener,based on the total amount of the grease composition.

Alternatively, it is preferable to contain 9 mass % to 18 mass % of thefluorine-based thickener, 0.5 mass % to 7 mass % of the urea-basedthickener, and 0.6 mass % to 3.6 mass % of the sodium soap thickener,based on the total amount of the grease composition.

It is preferable that the total amount of the fluorine-based thickener,the urea-based thickener and at least one soap-based thickener selectedfrom the group consisting of a calcium complex soap thickener, a calciumsoap thickener, a barium soap thickener, a magnesium soap thickener anda sodium soap thickener (the total amount of the thickeners) is 10 mass% to 30 mass %, particularly 10 mass % to 20 mass %, based on the totalamount of the grease composition.

<Fluorine-Based Thickener>

As the fluorine-based thickener, fluororesin particles are preferred,and for example, particles of polytetrafluoroethylene (PTFE) arepreferably used. PTFE is a polymer of tetrafluoroethylene and isrepresented by the general formula: [C₂F₄]_(n) (n: degree ofpolymerization).

Other examples of the fluorine-based thickener that can be adoptedinclude a perfluoroethylene propylene copolymer (FEP), an ethylenetetrafluoroethylene copolymer (ETFE), and a tetrafluoroethyleneperfluoroalkyl vinyl ether copolymer (PFA).

The size of the PTFE particles is not particularly limited, and forexample, polytetrafluoroethylene having an average particle size of 0.5μm to 100 μm can be used. The shape of the PTFE particles is notparticularly limited, and may be spherical, polyhedral, needle-like, orother shapes.

The fluorine-based thickener is preferably used in an amount of 9 mass %to 18 mass % based on the total amount of the grease composition.

<Urea-Based Thickener>

Since the urea compound is excellent in both heat resistance and waterresistance, and is particularly excellent in stability at a hightemperature, it is suitably used as a thickener for the parts subjectedto a high temperature environment.

A urea compound such as a diurea compound, a triurea compound, and apolyurea compound can be used as the urea-based thickener. Particularly,from the viewpoint of heat resistance and acoustic characteristic(quietness), it is preferable to use a diurea compound. The type of theurea compound preferably includes at least one of an aliphatic-aromaticurea, an alicyclic-aliphatic urea and an aliphatic urea.

Urea compounds conventionally known can be used as the above mentionedurea-based thickeners.

Among these urea compounds, the diurea compound represented by thefollowing General Formula (1) is a urea-based thickener suitable for anembodiment according to the present invention.

R₁—NHCONH—R₂—NHCONH—R₃  (1)

-   -   In the above Formula (1), R₁ and R₃ each independently represent        a monovalent aliphatic hydrocarbon group, a monovalent alicyclic        hydrocarbon group or a monovalent aromatic hydrocarbon group,        and at least one of R₁ and R₃ represents a monovalent aliphatic        hydrocarbon group or a monovalent alicyclic hydrocarbon group.

In addition, R₂ represents a divalent aromatic hydrocarbon group.

Examples of the monovalent aliphatic hydrocarbon group include a linearor branched, saturated or unsaturated alkyl group having 6 to 26 carbonatoms.

Examples of the monovalent alicyclic hydrocarbon group include acycloalkyl group having 5 to 12 carbon atoms.

In addition, examples of the aromatic hydrocarbon group include amonovalent or divalent aromatic hydrocarbon group having 6 to 20 carbonatoms.

The urea compound used as the urea-based thickener can be synthesizedusing an amine compound and an isocyanate compound.

Examples of the amine compound to be used here include: aliphatic aminesrepresented by hexylamine, octylamine, dodecylamine, hexadecylamine,octadecylamine, stearylamine, oleylamine or the like; cycloaliphaticamines represented by cyclohexylamine or the like; and aromatic aminesrepresented by aniline, p-toluidine, ethoxyphenylamine or the like.

Examples of the isocyanate compound include: aromatic diisocyanates suchas phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate,and diphenylmethane diisocyanate; and aliphatic diisocyanates such asoctadecane diisocyanate, decane diisocyanate, and hexane diisocyanate.

Among these, it is preferable to use an aliphatic-aromatic diureacompound obtained by using an aliphatic amine and an aromatic amine asan amine raw material and an aromatic diisocyanate to carry out thesynthesis.

When an aromatic diurea compound obtained from an aromatic monoamine andan aromatic diisocyanate is used as a urea-based thickener, there is apossibility of causing a1 noise, so its use should be carefullyconsidered.

The urea-based thickener is preferably used in an amount of 0.5 mass %to 7 mass % based on the total amount of the grease composition.

<Soap-Based Thickener>

A soap-based thickener is used in an embodiment according to the presentinvention, in addition to the above fluorine-based thickener andurea-based thickener.

In an embodiment according to the present invention, a calcium complexsoap thickener, a calcium soap thickener, a barium soap thickener, amagnesium soap thickener, and a sodium soap thickener can be used as thesoap-based thickener.

<Calcium Complex Soap Thickener>

It is preferable to use a calcium complex soap having improved heatresistance in an embodiment according to the present invention. Forexample, a calcium complex soap of a higher fatty acid and a lower fattyacid, a calcium complex soap containing a calcium salt of a dibasic acidand a fatty acid, or the like can be used.

Among these, it is preferable to use a calcium complex soap of analiphatic dicarboxylic acid and a monoamide monocarboxylic acid, as thecalcium complex soap thickener to be used in the grease compositionaccording to an embodiment of the present invention.

A saturated or unsaturated dicarboxylic acid having 2 to 20 carbon atomsis used as the aliphatic dicarboxylic acid.

Examples of the saturated dicarboxylic acid include an oxalic acid, amalonic acid, a succinic acid, a methylsuccinic acid, a glutaric acid,an adipic acid, a pimelic acid, a suberic acid, an azelaic acid, asebacic acid, a nonamethylenedicarboxylic acid, a decamethylenedicarboxylic acid, an undecane dicarboxylic acid, a dodecanedicarboxylic acid, a tridecane dicarboxylic acid, a tetradecanedicarboxylic acid, a pentadecane dicarboxylic acid, a hexadecanedicarboxylic acid, a heptadecane dicarboxylic acid, and an octadecanedicarboxylic acid. Preferably used are an adipic acid, a pimelic acid, asuberic acid, an azelaic acid, a sebacic acid, anonamethylenedicarboxylic acid, a decamethylene dicarboxylic acid, anundecane dicarboxylic acid, a dodecane dicarboxylic acid, a tridecanedicarboxylic acid, a tetradecane dicarboxylic acid, a pentadecanedicarboxylic acid, a hexadecane dicarboxylic acid, a heptadecanedicarboxylic acid, and an octadecane dicarboxylic acid.

In addition, as the unsaturated dicarboxylic acid, for example, a maleicacid, a fumaric acid, alkenyl succinic acids such as a 2-methylenesuccinic acid, a 2-ethylene succinic acid, and a 2-methylene glutaricacid are used.

These saturated or unsaturated dicarboxylic acids may be used alone orin combination of two or more.

Examples of the monoamide monocarboxylic acid include those in which onecarboxyl group in the aliphatic dicarboxylic acid is amidated.

At this time, examples of the amine for amidating the carboxyl groupinclude: aliphatic primary amines such as butylamine, amylamine,hexylamine, heptylamine, octylamine, nonylamine, decylamine,laurylamine, myristylamine, palmitylamine, stearylamine, andbehenylamine; aliphatic secondary amines such as dipropylamine,diisopropylamine, dibutylamine, diamylamine, dilaurylamine,monomethyllaurylamine, distearylamine, monomethylstearylamine,dimyristylamine, and dipalmitylamine; aliphatic unsaturated amines suchas allylamine, diallylamine, oleylamine, and dioleylamine; alicyclicamines such as cyclopropylamine, cyclobutylamine, cyclopentylamine, andcyclohexylamine; and aromatic amines such as aniline, methylaniline,ethylaniline, benzylamine, dibenzylamine, diphenylamine, andα-naphthylamine.

Among these, hexylamine, heptylamine, octylamine, nonylamine,decylamine, laurylamine, myristylamine, palmitylamine, stearylamine,behenylamine, dibutylamine, diamylamine, monomethyllaurylamine,monomethylstearylamine, and oleylamine are preferably used.

A commercially available product can suitably be used as the calciumcomplex soap thickener.

In addition, a calcium complex soap, obtained by adding an aliphaticdicarboxylic acid and a monoamide monocarboxylic acid to anon-fluorine-based base oil, performing heating and stirring under atemperature at which stirring is possible, the reaction proceedsefficiently, and the base oil does not deteriorate (for example, about80° C. to 180° C.), and adding calcium hydroxide thereto, may also beused.

The calcium complex soap thickener is preferably used in an amount of0.3 mass % to 3 mass % based on the total amount of the greasecomposition.

<Calcium Soap Thickener, Barium Soap Thickener, Magnesium SoapThickener, and Sodium Soap Thickener>

A metal salt of an aliphatic monocarboxylic acid, that is, a calciumsalt, a barium salt, a magnesium salt or a sodium salt of an aliphaticmonocarboxylic acid, can be used as the calcium soap thickener, thebarium soap thickener, the magnesium soap thickener and the sodium soapthickener.

The aliphatic carboxylic acid may be any of linear, branched, saturatedand unsaturated, and generally fatty acids having about 2 to 30 carbonatoms, for example, 12 to 24 carbon atoms can be used. Specific examplethereof include: saturated fatty acids such as a butyric acid, a caproicacid, a caprylic acid, a pelargonic acid, a capric acid, a lauric acid,a myristic acid, a palmitic acid, a stearic acid, and a behenic acid;and unsaturated fatty acids such as an oleic acid, a linoleic acid, alysic acid, and a ricinoleic acid (ricinoleic acid).

Among these, a calcium salt, a barium salt, a magnesium salt, a sodiumsalt of the stearic acid, the lauric acid and the ricinoleic acid can beused as representative examples of the calcium soap thickener, thebarium soap thickener, the magnesium soap thickener and the sodium soapthickener.

Commercially available products of the calcium soap thickener, thebarium soap thickener, the magnesium soap thickener and the sodium soapthickener can be suitably used.

The calcium soap thickener is preferably used in an amount of 0.3 mass %to 3 mass % based on the total amount of the grease composition.

In addition, with regard to the barium soap thickener, the magnesiumsoap thickener and the sodium soap thickener, the barium soap thickeneris preferably used in an amount of 0.6 mass % to 3.6 mass % based on thetotal amount of the grease composition; the magnesium soap thickener ispreferably used in an amount of 0.6 mass % to 3.6 mass % based on thetotal amount of the grease composition; and the sodium soap thickener ispreferably used in an amount of 0.6 mass % to 3.6 mass % based on thetotal amount of the grease composition.

<Other Additives>

In addition to the above essential components, the grease compositionmay contain additives usually used in the grease composition, ifnecessary, within a range not hindering the effects of the presentinvention.

Examples of the additives include an antioxidant, an extreme pressureagent, a metal deactivator, a friction inhibitor (anti-wear agent), arust inhibitor, an oiliness improver, a viscosity index improver, and aviscosifier.

In the case of containing the other additives, the total amount of theadditives is generally 0.1 mass % to 10 mass % based on the total amountof the grease composition.

Examples of the antioxidant include: hindered phenol-based antioxidantssuch as octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate,pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate],2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine,1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl) benzene,triethylene glycol bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], andN,N′-hexamethylenebis(3,5-di-t-butyl-4-hydroxy-hydrocinnamide);phenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and4,4-methylenebis(2,6-di-t-butylphenol); amine-based antioxidants such astriphenylamine, phenyl-α-naphthylamine, alkylatedphenyl-α-naphthylamine, phenothiazine, and alkylated phenothiazine.

Examples of the extreme pressure agent include: phosphorus compoundssuch as phosphate ester, phosphite ester, and phosphate ester aminesalt; sulfur compounds such as sulfides and disulfides; chlorinatedcompounds such as chlorinated paraffin and chlorinated diphenyl; andmetal salts of a sulfur compound such as zinc dialkyldithiophosphate andmolybdenum dialkyldithiocarbamate.

Examples of the metal deactivator include benzotriazole and sodiumnitrite.

Examples of the anti-wear agent include tricresyl phosphate and polymeresters.

Examples of the polymer esters include esters of aliphatic monovalentcarboxylic acids and divalent carboxylic acids with polyhydric alcohols.Specific examples of the polymer esters include, but are not limited to,PRIOLUBE (registered trademark) series manufactured by Croda Japan KK.

The grease composition according to an embodiment of the presentinvention can be obtained by mixing the above various base oils andvarious thickeners at a predetermined proportion and optionally addingother additives.

The grease composition may also be produced by blending three types ofgreases, i.e., a fluorine-based grease containing a fluorine-based baseoil and a fluorine-based thickener, a urea-based grease containing anon-fluorine-based base oil and a urea-based thickener, and a soap-basedgrease (a calcium complex soap grease, a calcium soap grease, a bariumsoap grease, a magnesium soap grease, or a sodium soap grease)containing a non-fluorine-based base oil and a soap-based thickener (acalcium complex soap thickener, a calcium soap thickener, a barium soapthickener, a magnesium soap thickener, or a sodium soap thickener), withother additives if desired. Alternatively, the grease composition mayalso be produced by blending one or two of the above base greases withthe remaining base oil and thickener and, if desired, other additives.

Usually, the content of the thickener based on the base grease is about10 mass % to 30 mass %. For example, in the three types of base greases,the content of each thickener based on the respective base grease is asfollows: fluorine-based thickener: 15 mass % to 30 mass %; urea-basedthickener: 10 mass % to 20 mass %; and soap-based thickener (calciumcomplex soap thickener, calcium soap thickener, barium soap thickener,magnesium soap thickener, or sodium soap thickener): 10 mass % to 20mass %.

The rolling bearing of the present embodiment is particularly preferablyused as a rolling bearing of small motors (e.g., brushless motors andfan motors) of automobiles, household electric appliances, informationequipment and the like.

The invention according to the present disclosure is not limited to theembodiments and specific examples described in this specification andvarious changes and modifications can be made within the scope of thetechnical idea described in the claims.

For example, although the rolling bearing is cited as a ball bearing inthe above embodiment, the present invention is not limited to this butcan be applied to other rolling bearings, for example, roller bearings.

Examples

Hereinafter, the embodiments of the invention according to the presentdisclosure will be described in more detail by examples. However, thepresent invention is not limited thereto.

[Evaluation on Grease Composition]

Grease compositions to be used in Examples 1 to 66 and ComparativeExamples 1 to 51 were prepared with the blending amounts shown in thefollowing tables.

The details and the abbreviations of each component used for thepreparation of the grease are as follows.

(a) Base Oil

(a1) fluorine-based base oil: linear perfluoropolyether (PFPE)

(a2) non-fluorine-based base oil: synthetic oil 1, mixed oil ofpolyalphaolefin oil and ester oil

(a3) non-fluorine-based base oil: synthetic oil 2, polyalphaolefin oil

(b) Thickener

(b1) fluorine-based thickener: PTFE (polytetrafluoroethylene, particlesize 10 μm to 25 μm

(b2-1) urea-based thickener: urea compound containing aliphatic-aromaticurea

(b2-2) urea-based thickener: urea compound containingalicyclic-aliphatic urea

(b2-3) urea-based thickener: urea compound containing aliphatic urea

(b3-1) Ca complex soap thickener: calcium complex soap of aliphaticdicarboxylic acid and monoamide monocarboxylic acid

(b3-2) Ca soap thickener: 12OHCa soap (calcium 12-hydroxystearate)

(b3-3) Ba soap thickener: 12OHBa soap (barium 12-hydroxystearate)

(b3-4) Mg soap thickener: 12OHMg soap (magnesium 12-hydroxystearate)

(b3-5) Na soap thickener: 12OHNa soap (sodium 12-hydroxystearate)

(b3-6) Li soap thickener: 12OHLi soap (lithium 12-hydroxystearate)

Generally, the urea-based thickeners (b2-1 to b2-3) are added in anamount of 10 mass % to 20 mass % based on the total amount of the basegrease containing the urea-based thickener and the non-fluorine-basedbase oil: synthetic oil 1 (a2). The Ca complex soap thickener (b3-1),the Ca soap thickener (b3-2), the Ba soap thickener (b3-3), the Mg soapthickener (b3-4), the Na soap thickener (b3-5), or the Li soap thickener(b3-6) is added in an amount of 10 mass % to 20 mass % based on thetotal amount of the base grease containing the complex soap thickener,the Ca soap thickener, the Ba soap thickener, the Mg soap thickener, theNa soap thickener, or the Li soap thickener and the non-fluorine-basedbase oil: synthetic oil 2 (a3).

(c) Other Additives, Antioxidant: Amine Antioxidant; Extreme PressureAgent: Phosphorus Extreme Pressure Additive

The other additives were added such that the total amount of the aboveantioxidant and extreme pressure agent was 3 mass % based on the greasecomposition (total mass) of Examples and Comparative Example.

With respect to the characteristics of the obtained grease composition,a heat resistance test and a load resistance test were performed usingthe following procedures, and the acoustic characteristics wereevaluated.

<Test Methods> 1. Heat Resistance Test

The test grease composition was filled in a steel shielded ball bearing(inner diameter 8 mm, outer diameter 22 mm, width 7 mm) at 25% to 35% ofthe bearing volume. The ball bearing was set in a housing and a preloadof 39 N was applied to the outer ring from the axial direction. Then ashaft was inserted into the inner diameter of the bearing and the shaftwas connected to a rotation shaft of a test motor, so that the innerring of the ball bearing was arranged to be rotated.

Next, the housing was heated to 180° C., the ball bearing was rotated ata test temperature of 180° C. and a rotation speed of 21,000 rpm for 200hours, and then subjected to an acoustic evaluation test according tothe following procedures. Each test grease of examples and comparativeexample was tested three times to obtain the average value.

2. Load Resistance Test

The test grease composition was filled in a steel shielded ball bearing(inner diameter 8 mm, outer diameter 22 mm, width 7 mm) at 25% to 35% ofthe bearing volume. The ball bearing was set in a housing and a preloadof 500 N was applied to the outer ring from the axial direction. Then ashaft was inserted into the inner diameter of the bearing and the shaftwas connected to a rotation shaft of a test motor, so that the innerring of the ball bearing was arranged to be rotated.

Next, the ball bearing was rotated at room temperature at a rotationspeed of 3,000 rpm for 100 hours, and then subjected to an acousticevaluation test according to the following procedures. Each test greaseof examples and comparative example was tested three times to obtain theaverage value.

<Acoustic Evaluation>

The acoustic performance of the ball bearing using the test greasecomposition was evaluated by measuring the Anderon value of M band (300Hz to 1800 Hz) using an Anderon meter.

In detail, after each ball bearing was rotated for a predetermined timefollowing the above procedures, under the preload, temperature conditionand rotation speed as described above, the speed-type pickup was broughtinto contact with the outer circumference of the outer ring of the ballbearing in the radial direction, the mechanical vibration transmitted tothe outer ring was detected to calculate the Anderon value, and theacoustic performance in each test was evaluated based on the followingcriteria (maximum measurable value of Anderon value: 50). The sound inthe frequency of the M band which corresponds to 300 Hz to 1800 Hz isconsidered an unpleasant sound for human.

(Evaluation Criteria)

In the test conditions of Examples, significant wear is observed whenthe Anderon value is 15 or more, so that less than 15 is evaluated assuitable.

-   -   A: average Anderon value is less than 15    -   N: average Anderon value is 15 or more

The results are shown in Tables 1 to 9 and in FIGS. 2 to 7. Blendingamount in the table in terms of mass % is a value based on the totalmass of the grease composition.

TABLE 1 Ca complex soap Comparative Example (mentioned Example (Cacomplex soap) later) Blending amount (mass %) 1 2 3 4 5 6 7 8 9 10 11 1213 14 15 17 18 Base oil (a1) Fluorine- 71.2 62.1 62.1 62.1 62.1 55.255.2 55.2 55.2 39.2 39.2 39.2 39.2 55.2 55.2 55.2 39.2 based (a2) Non-3.4 14.7 13 8.8 0.2 22.1 20.4 16.2 7.6 37.4 33.2 28.9 24.6 11.9 11.9 3.420.4 fluorine-based (a3) Non- 3.4 1.7 3.4 7.6 16.2 1.7 3.4 7.6 16.2 3.47.6 11.9 16.2 11.9 11.9 20.4 20.4 fluorine-based Thickener (b1)Fluorine- 17.8 15.6 15.6 15.6 15.6 13.8 13.8 13.8 13.8 9.8 9.8 9.8 9.813.8 13.8 13.8 9.8 based (b2-1) Urea- 0.6 2.6 2.3 1.6 0.5 3.9 3.6 2.91.3 6.6 5.9 5.1 4.3 0.6 3.6 based (b2-2) Urea- 2.1 based (b2-3) Urea-2.1 based (b3-1) Ca 0.6 0.3 0.6 1.3 2.4 0.3 0.6 1.3 2.9 0.6 1.3 2.1 2.92.1 2.1 3.6 3.6 complex soap (b3-2) Ca soap (b3-3) Ba soap (b3-4) Mgsoap (b3-5) Na soap (b3-6) Li soap Additive 3.0 3.0 3.0 3.0 3.0 3.0 3.03.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Heat Anderon value 8.5 8.2 8.59.4 10 6.5 6.8 4.3 6.0 2.0 2.5 3.0 4.0 5.5 4.8 30 21 resistanceDetermination A A A A A A A A A A A A A A A N N evaluation Load Anderonvalue 9.5 14 10.4 9.5 5.2 12 9.4 4.3 6.0 8.0 3.0 2.0 2.0 5.5 4.8 3.0 13resistance Determination A A A A A A A A A A A A A A A A A evaluation

TABLE 2 Ca soap Comparative Example (mentioned Example (Ca soap) later)Blending amount (mass %) 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 2223 Base oil (a1) Fluorine- 71.2 62.1 62.1 62.1 62.1 55.2 55.2 55.2 55.239.2 39.2 39.2 39.2 55.2 55.2 55.2 39.2 based (a2) Non- 3.4 14.7 13 8.80.2 22.1 20.4 16.2 7.6 39.1 37.4 33.2 24.6 11.9 11.9 3.4 20.4fluorine-based (a3) Non- 3.4 1.7 3.4 7.6 16.2 1.7 3.4 7.6 16.2 1.7 3.47.6 16.2 11.9 11.9 20.4 20.4 fluorine-based Thickener (b1) Fluorine-17.8 15.6 15.6 15.6 15.6 13.8 13.8 13.8 13.8 9.8 9.8 9.8 9.8 13.8 13.813.8 9.8 based (b2-1) Urea- 0.6 2.6 2.3 1.6 0.5 3.9 3.6 2.9 1.3 6.9 6.65.9 4.3 0.6 3.6 based (b2-2) Urea- 2.1 based (b2-3) Urea- 2.1 based(b3-1) Ca complex soap (b3-2) Ca soap 0.6 0.3 0.6 1.3 2.4 0.3 0.6 1.32.9 0.3 0.6 1.3 2.9 2.1 2.1 3.6 3.6 (b3-3) Ba soap (b3-4) Mg soap (b3-5)Na soap (b3-6) Li soap Additive 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.03.0 3.0 3.0 3.0 3.0 3.0 3.0 Heat Anderon value 14 7.2 7.5 9 10 9.4 127.8 9.5 9 9.5 10 12 4.5 5.8 25 20 resistance Determination A A A A A A AA A A A A A A A N N evaluation Load Anderon value 10.4 12 9.5 8 5 14 143.2 8.2 11 8.5 9.2 9.6 5.2 5.3 7.8 11 resistance Determination A A A A AA A A A A A A A A A A A evaluation

TABLE 3 Ba soap Comparative Comparative Example Example (mentioned(mentioned later) Example (Ba soap) later) Blending amount (mass %) 2627 28 31 32 33 34 35 36 37 38 39 40 41 42 29 30 Base oil (a1) Fluorine-55.2 62.1 39.2 71.2 62.1 62.1 62.1 55.2 55.2 55.2 55.2 39.2 39.2 39.239.2 39.2 39.2 based (a2) Non- 22.1 14.7 39.1 3.4 13 8.8 0.2 20.4 16.27.6 3.4 37.4 33.2 24.6 20.4 16.6 10.2 fluorine-based (a3) Non- 1.7 1.71.7 3.4 3.4 7.6 16.2 3.4 7.6 16.2 20.4 3.4 7.6 16.2 20.4 24.2 30.6fluorine-based Thickener (b1) Fluorine- 13.8 15.6 9.8 17.8 15.6 15.615.6 13.8 13.8 13.8 13.8 9.8 9.8 9.8 9.8 9.8 9.8 based (b2-1) Urea- 3.92.6 6.9 0.6 2.3 1.6 0.5 3.6 2.9 1.3 0.6 6.6 5.9 4.3 3.6 2.9 1.8 based(b2-2) Urea- based (b2-3) Urea- based (b3-1) Ca complex soap (b3-2) Casoap (b3-3) Ba soap 0.3 0.3 0.3 0.6 0.6 1.3 2.4 0.6 1.3 2.9 3.6 0.6 1.32.9 3.6 4.3 5.4 (b3-4) Mg soap (b3-5) Na soap (b3-6) Li soap Additive3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 HeatAnderon value 7.2 5.5 4.3 5.5 6.5 8 7 6 5.2 2.5 5 4.8 4.4 5.4 6.5 16 50resistance Determination A A A A A A A A A A A A A A A N N evaluationLoad Anderon value 18 16 16 4 6 6.5 7 5 2.5 4 4.5 7.0 6.6 5.2 6 5.5 5.5resistance Determination N N N A A A A A A A A A A A A A A evaluation

TABLE 4 Mg soap Comparative Comparative Example Example (mentioned(mentioned later) Example (Mg soap) later) Blending amount (mass %) 3334 35 43 44 45 46 47 48 49 50 51 52 53 54 36 37 Base oil (a1) Fluorine-55.2 62.1 39.2 71.2 62.1 62.1 62.1 55.2 55.2 55.2 55.2 39.2 39.2 39.239.2 39.2 39.2 based (a2) Non- 22.1 14.7 39.1 3.4 13 8.8 0.2 20.4 16.27.6 3.4 37.4 33.2 24.6 20.4 16.6 10.2 fluorine-based (a3) Non- 1.7 1.71.7 3.4 3.4 7.6 16.2 3.4 7.6 16.2 20.4 3.4 7.6 16.2 20.4 24.2 30.6fluorine-based Thickener (b1) Fluorine- 13.8 15.6 9.8 17.8 15.6 15.615.6 13.8 13.8 13.8 13.8 9.8 9.8 9.8 9.8 9.8 9.8 based (b2-1) Urea- 3.92.6 6.9 0.6 2.3 1.6 0.5 3.6 2.9 1.3 0.6 6.6 5.9 4.3 3.6 2.9 1.8 based(b2-2) Urea- based (b2-3) Urea- based (b3-1) Ca complex soap (b3-2) Casoap (b3-3) Ba soap (b3-4) Mg soap 0.3 0.3 0.3 0.6 0.6 1.3 2.4 0.6 1.32.9 3.6 0.6 1.3 2.9 3.6 4.3 5.4 (b3-5) Na soap (b3-6) Li soap Additive3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 HeatAnderon value 9.5 4.5 4 6.5 5 6 4.5 6.5 4.5 4.5 9 4.6 5.5 6.5 8 18 50resistance Determination A A A A A A A A A A A A A A A N N evaluationLoad Anderon value 17 20 17 5 6 7 7 7.5 7.8 3 6.0 8 6.5 6.5 6 6.5 7resistance Determination N N N A A A A A A A A A A A A A A evaluation

TABLE 5 Na soap Comparative Comparative Example Example (mentioned(mentioned later) Example (Na soap) later) Blending amount (mass %) 4041 42 55 56 57 58 59 60 61 62 63 64 65 66 43 44 Base oil (a1) Fluorine-55.2 62.1 39.2 71.2 62.1 62.1 62.1 55.2 55.2 55.2 55.2 39.2 39.2 39.239.2 39.2 39.2 based (a2) Non- 22.1 14.7 39.1 3.4 13 8.8 0.2 20.4 16.27.6 3.4 37.4 33.2 24.6 20.4 16.6 10.2 fluorine-based (a3) Non- 1.7 1.71.7 3.4 3.4 7.6 16.2 3.4 7.6 16.2 20.4 3.4 7.6 16.2 20.4 24.2 30.6fluorine-based Thickener (b1) Fluorine- 13.8 15.6 9.8 17.8 15.6 15.615.6 13.8 13.8 13.8 13.8 9.8 9.8 9.8 9.8 9.8 9.8 based (b2-1) Urea- 3.92.6 6.9 0.6 2.3 1.6 0.5 3.6 2.9 1.3 0.6 6.6 5.9 4.3 3.6 2.9 1.8 based(b2-2) Urea- based (b2-3) Urea- based (b3-1) Ca complex soap (b3-2) Casoap (b3-3) Ba soap (b3-4) Mg soap (b3-5) Na soap 0.3 0.3 0.3 0.6 0.61.3 2.4 0.6 1.3 2.9 3.6 0.6 1.3 2.9 3.6 4.3 5.4 (b3-6) Li soap Additive3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 HeatAnderon value 6.8 2.5 3.1 7 3 3 4 6.5 7.2 4.5 7.5 3.5 3.8 4.2 7 20 50resistance Determination A A A A A A A A A A A A A A A N N evaluationLoad Anderon value 17 18 18 7 6 5 6 5.5 6.2 6 5.8 7 7.4 5.2 6 7.5 7.5resistance Determination N N N A A A A A A A A A A A A A A evaluation

TABLE 6 Comparative Example (two Comparative Example (one type) types)Blending amount (mass %) 1 2 3 4 5 6 7 8 9 10 11 12 13 Base oil (a1)Fluorine- 77.6 62.1 54.7 39.2 based (a2) Non-fluorine- 82.4 82.4 82.416.4 24.2 40.8 based (a3) Non-fluorine- 82.4 82.4 82.4 82.4 82.4 82.4based Thickener (b1) Fluorine- 19.4 15.6 13.8 9.8 based (b2-1)Urea-based 14.6 2.9 4.3 7.2 (b2-2) Urea-based 14.6 (b2-3) Urea-based14.6 (b3-1) Ca complex 14.6 soap (b3-2) Ca soap 14.6 (b3-3) Ba soap 14.6(b3-4) Mg soap 14.6 (b3-5) Na soap 14.6 (b3-6) Li soap 14.6 Additive 3.03.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Heat Anderon value 8.032 30 35 50 50 50 50 50 50 6 6.3 4 resistance Determination A N N N N NN N N N A A A evaluation Load Anderon value 50 1.3 1.4 1.2 1.5 7.8 2.56.0 3.5 3.2 50 50 20 resistance Determination N A A A A A A A A A N N Nevaluation

TABLE 7 Comparative Example Comparative Example Comparative Example (Cacomplex soap) (Ca soap) (Ba soap) Blending amount (mass %) 14 15 16 1718 19 20 21 22 23 24 25 26 27 28 29 30 Base oil (a1) Fluorine- 62.1 54.739.2 55.2 39.2 62.1 54.7 39.2 55.2 39.2 54.7 62.1 55.2 62.1 39.2 39.239.2 based (a2) Non- 3.4 20.4 3.4 20.4 22.1 14.7 39.1 16.6 10.2fluorine- based (a3) Non- 16.4 24.2 40.8 20.4 20.4 16.4 24.2 40.8 20.420.4 24.2 16.4 1.7 1.7 1.7 24.2 30.6 fluorine- based Thickener (b1)Fluorine- 15.6 13.8 9.8 13.8 9.8 15.6 13.8 9.8 13.8 9.8 13.8 15.6 13.815.6 9.8 9.8 9.8 based (b2-1) Urea- 0.6 3.6 0.6 3.6 3.9 2.6 6.9 2.9 1.8based (b2-2) Urea- based (b2-3) Urea- based (b3-1) Ca 2.9 4.3 7.2 3.63.6 complex soap (b3-2) Ca soap 2.9 4.3 7.2 3.6 3.6 (b3-3) Ba soap 4.32.9 0.3 0.3 0.3 4.3 5.4 (b3-4) Mg soap (b3-5) Na soap (b3-6) Li soapAdditive 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.03.0 Heat Anderon value 18 50 45 30 21 16 50 50 25 20 25 20 7.2 5.5 4.316 50 resistance Determination N N N N N N N N N N N N A A A N Nevaluation Load Anderon value 6 3.0 3 3.0 13 6 7.0 5 7.8 11 1.6 9 18 1616 5.5 5.5 resistance Determination A A A A A A A A A A A A N N N A Aevaluation

TABLE 8 Comparative Example (Mg soap) Comparative Example (Na soap)Blending amount (mass %) 31 32 33 34 35 36 37 38 39 40 41 42 43 44 Baseoil (a1) Fluorine- 54.7 62.1 55.2 62.1 39.2 39.2 39.2 54.7 62.1 55.262.1 39.2 39.2 39.2 based (a2) Non-fluorine- 22.1 14.7 39.1 16.6 10.222.1 14.7 39.1 16.6 10.2 based (a3) Non-fluorine- 24.2 16.4 1.7 1.7 1.724.2 30.6 24.2 16.4 1.7 1.7 1.7 24.2 30.6 based Thickener (b1) Fluorine-13.8 15.6 13.8 15.6 9.8 9.8 9.8 13.8 15.6 13.8 15.6 9.8 9.8 9.8 based(b2-1) Urea-based 3.9 2.6 6.9 2.9 1.8 3.9 2.6 6.9 2.9 1.8 (b2-2)Urea-based (b2-3) Urea-based (b3-1) Ca complex soap (b3-2) Ca soap(b3-3) Ba soap (b3-4) Mg soap 4.3 2.9 0.3 0.3 0.3 4.3 5.4 (b3-5) Na soap4.3 2.9 0.3 0.3 0.3 4.3 5.4 (b3-6) Li soap Additive 3.0 3.0 3.0 3.0 3.03.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Heat Anderon value 50 25 9.5 4.5 418 50 18 20 6.8 2.5 3.1 20 50 resistance Determination N N A A A N N N NA A A N N evaluation Load Anderon value 6.0 8 17 20 17 6.5 7 2.0 7 17 1818 7.5 7.5 resistance Determination A A N N N A A A A N N N A Aevaluation

TABLE 9 Comparative Example (Li soap) Blending amount (mass %) 45 46 4748 49 50 51 Base oil (a1) Fluorine- 54.7 55.2 55.2 55.2 55.2 55.2 55.2based (a2) Non-fluorine- 22.1 20.4 16.2 11.9 7.6 3.4 based (a3)Non-fluorine- 24.2 1.7 3.4 7.6 11.9 16.2 20.4 based Thickener (b1)Fluorine- 13.8 13.8 13.8 13.8 13.8 13.8 13.8 based (b2-1) Urea-based 3.93.6 2.9 2.1 1.3 0.6 (b2-2) Urea-based (b2-3) Urea-based (b3-1) Cacomplex soap (b3-2) Ca soap (b3-3) Ba soap (b3-4) Mg soap (b3-5) Na soap(b3-6) Li soap 4.3 0.3 0.6 1.3 2.1 2.9 3.6 Additive 3.0 3.0 3.0 3.0 3.03.0 3.0 Heat Anderon value 50 9.5 11 30 32 30 35 resistanceDetermination N A A N N N N evaluation Load Anderon value 50 50 50 50 5050 50 resistance Determination N N N N N N N evaluation

As described above, FIG. 2 shows the results of the respective Anderonvalues of the M band after the heat resistance test and load resistancetest for grease compositions (Examples 1 to 15, Comparative Examples 11to 13, Comparative Example 15, Comparative Example 17, and ComparativeExample 18) in which the content of a fluorine-based thickener is 17.8mass % to 9.8 mass % (blending amount of the fluorine-based grease basedon the total amount of the grease composition: 90 mass % to 49 mass %),the content of the urea-based thickener is 0 mass % to 7.2 mass %(blending amount of the urea-based grease: 0 mass % to 48 mass %), andthe content of the calcium complex soap thickener is 0 mass % to 4.3mass % (blending amount of the calcium complex soap grease: 0 mass % to29 mass %). In the graph shown in FIG. 2, the horizontal axis representsthe content (mass %) of the calcium complex soap thickener based on thetotal amount of grease composition, and the vertical axis represents theAnderon value of M band after the tests. In FIG. 2, the broken lineparallel to the horizontal axis indicates an Anderon value of 15, andthe range indicated by the arrow parallel to the horizontal axisindicates the content range of the calcium complex soap thickener whichcan obtain good acoustic characteristic in both the load resistance testand the heat resistance test.

As shown in FIG. 2, it is confirmed that when the content of the calciumcomplex soap thickener is in the range of 0.3 mass % to 3 mass % basedon the total amount of the grease composition, good acousticcharacteristic can be obtained in both the load resistance test (highload test: ▪ (black square) in FIG. 2, and the same for other graphs)and the heat resistance test (high temperature and high speed test: ⋄(diamond) in FIG. 2, and the same for other graphs). For the acousticcharacteristic after the load resistance test, as the content of thecalcium complex soap thickener becomes smaller than 0.3 mass %, theAnderon value rapidly increases; on the other hand, when the content ofthe calcium complex soap thickener is larger than 0.3 mass %, theAnderon value is less than 15 and the acoustic characteristics arestable in a good state. For the acoustic characteristics after the heatresistance test, as the content of the calcium complex soap thickenerbecomes larger than 3 mass %, the Anderon value rapidly increases; onthe other hand, when the content of the calcium complex soap thickeneris smaller than 3 mass %, the Anderon value is less than 15 and theacoustic characteristics are stable in a good state. Therefore, goodacoustic characteristic can be obtained in both the load resistance testand the heat resistance test when the content of the calcium complexsoap thickener to be used in combination with the fluorine-basedthickener and the urea-based thickener is in the range of 0.3 mass % to3 mass %.

Similarly, FIG. 3 shows the results of the respective Anderon values ofthe M band after the heat resistance test and load resistance test forgrease compositions (Examples 16 to 30, Comparative Examples 11 to 13,Comparative Example 20, Comparative Example 22, and Comparative Example23) in which the content of the calcium soap thickener based on thetotal amount of the grease composition is 0 mass % to 4.3 mass %(blending amount of the calcium soap grease based on the total amount ofthe grease composition: 0 mass % to 29 mass %). In the graph shown inFIG. 3, the horizontal axis represents the content (mass %) of thecalcium soap thickener based on the total amount of grease composition,and the vertical axis represents the Anderon value of M band after thetests. In FIG. 3, the broken line attached parallel to the horizontalaxis indicates an Anderon value of 15, and the range indicated by thearrows provided parallel to the horizontal axis indicates the contentrange of the calcium soap thickener which can obtain good acousticcharacteristic in both the load resistance test and the heat resistancetest.

FIG. 4 shows the results of the respective Anderon values of the M bandafter the heat resistance test and load resistance test for greasecompositions (Examples 31 to 42, Comparative Examples 11 to 13,Comparative Example 24, and Comparative Examples 26 to 30) in which thecontent of the barium soap thickener based on the total amount of thegrease composition is in the range of 0 mass % to 5.4 mass % (blendingamount of the barium soap grease based on the total amount of the greasecomposition: 0 mass % to 36 mass %). In the graph shown in FIG. 4, thehorizontal axis represents the content (mass %) of the barium soapthickener based on the total amount of grease composition, and thevertical axis represents the Anderon value of M band after the tests. InFIG. 4, the broken line parallel to the horizontal axis indicates anAnderon value of 15, and the range indicated by the arrow parallel tothe horizontal axis indicates the content range of the barium soapthickener which can obtain good acoustic characteristic in both the loadresistance test and the heat resistance test.

FIG. 5 shows the results of the respective Anderon values of the M bandafter the heat resistance test and load resistance test for greasecompositions (Examples 43 to 54, Comparative Examples 11 to 13,Comparative Example 31, and Comparative Examples 33 to 37) in which thecontent of the magnesium soap thickener based on the total amount of thegrease composition is in the range of 0 mass % to 5.4 mass % (blendingamount of the magnesium soap grease based on the total amount of thegrease composition: 0 mass % to 36 mass %). In the graph shown in FIG.5, the horizontal axis represents the content (mass %) of the magnesiumsoap thickener based on the total amount of grease composition, and thevertical axis represents the Anderon value of M band after the tests. InFIG. 5, the broken line parallel to the horizontal axis indicates anAnderon value of 15, and the range indicated by the arrow parallel tothe horizontal axis indicates the content range of the magnesium soapthickener which can obtain good acoustic characteristics in both theload resistance test and the heat resistance test.

FIG. 6 shows the results of the respective Anderon values of the M bandafter the heat resistance test and load resistance test for greasecompositions (Examples 55 to 66, Comparative Examples 11 to 13,Comparative Example 38, and Comparative

Examples 40 to 44) in which the content of the sodium soap thickenerbased on the total amount of the grease composition is in the range of 0mass % to 5.4 mass % (blending amount of the sodium soap grease based onthe total amount of the grease composition: 0 mass % to 36 mass %). Inthe graph shown in FIG. 6, the horizontal axis represents the content(mass %) of the sodium soap thickener based on the total amount ofgrease composition, and the vertical axis represents the Anderon valueof M band after the tests. In FIG. 6, the broken line parallel to thehorizontal axis indicates an Anderon value of 15, and the rangeindicated by the arrow parallel to the horizontal axis indicates thecontent range of the sodium soap thickener which can obtain goodacoustic characteristics in both the load resistance test and the heatresistance test.

As shown in FIG. 3 to FIG. 6, it is confirmed that good acousticcharacteristic is obtained in both the load resistance test and the heatresistance test when, based on the total amount of the greasecomposition, the content of the calcium soap thickener is between 0.3mass % and 3 mass %, the content of the barium soap thickener is between0.6 mass % and 3.6 mass %, the content of the magnesium soap thickeneris between 0.6 mass % and 3.6 mass %, or the content of the sodium soapthickener is between 0.6 mass % and 3.6 mass %. The acousticcharacteristic shows the same tendency as the acoustic characteristic ofthe grease composition using the calcium complex soap thickener in FIG.2.

On the other hand, FIG. 7 shows the results of the respective Anderonvalues of the M band after the heat resistance test and load resistancetest for grease compositions (Comparative Example 11 to ComparativeExample 13, and Comparative Example 45 to Comparative Example 51) inwhich the content of the lithium soap thickener based on the totalamount of the grease composition is in the range of 0 mass % to 4.3 mass% (blending amount of the lithium soap grease based on the total amountof the grease composition: 0 mass % to 29 mass %). In the graph shown inFIG. 7, the horizontal axis represents the content (mass %) of thelithium soap thickener based on the total amount of grease composition,and the vertical axis represents the Anderon value of M band after thetests. In FIG. 7, the broken line parallel to the horizontal axisindicates an Anderon value of 15.

As shown in FIG. 7, it is confirmed that when the lithium soap thickeneris used as a thickener, in combination with the above thickeners, theacoustic characteristic of the load resistance test deteriorates, andthe acoustic characteristic of the heat resistance test alsodeteriorates as the content of the lithium soap thickener increases.

For the acoustic characteristic after the load resistance test, theAnderon value remains higher than 15, regardless of the content of thelithium soap thickener. In addition, for the acoustic characteristicsafter the heat resistance test, when the content of the lithium soapthickener is less than 0.6 mass %, the Anderon value is less than 15,but when the content of the lithium soap thickener is larger than 0.6mass %, the Anderon value is higher than 15. Accordingly, it isconfirmed that when the fluorine-based thickener and the urea-basedthickener are used in combination with the lithium soap thickener, goodacoustic characteristic cannot be obtained in neither the loadresistance test nor the heat resistance test.

As a result of the tests, in a grease composition containing thefluorine-based thickener, the urea-based thickener and the calciumcomplex soap thickener in a specific proportion, that is, a greasecomposition containing 9 mass % to 18 mass % of the fluorine-basedthickener, 0.5 mass % to 7 mass % of the urea-based thickener, and 0.3mass % to 3 mass % of the calcium complex soap thickener based on thetotal amount of the grease composition as shown in Table 1, the averageAnderon value is less than 15 and the acoustic performance is good inboth the heat resistance test (180° C., 21,000 rpm, preload: 39 N, 200hours rotation) and the load resistance test (room temperature, 3,000rpm, preload: 500 N, 100 hours rotation).

Similarly, the results show that, in a grease composition containing 9mass % to 18 mass % of the fluorine-based thickener, 0.5 mass % to 7mass %% of the urea-based thickener, and 0.3 mass % to 3 mass % of thecalcium soap thickener, based on the total amount of the greasecomposition, as shown in Table 2; a grease composition containing 9 mass% to 18 mass % of the fluorine-based thickener, 0.5 mass % to 7 mass %of the urea-based thickener, and 0.6 mass % to 3.6 mass % of the bariumsoap thickener, based on the total amount of the grease composition, asshown in Table 3; a grease composition containing 9 mass % to 18 mass %of the fluorine-based thickener, 0.5 mass % to 7 mass % of theurea-based thickener, and 0.6 mass % to 3.6 mass % of the magnesium soapthickener, based on the total amount of the grease composition as shownin Table 4; and a grease composition containing 9 mass % to 18 mass % ofthe fluorine-based thickener, 0.5 mass % to 7 mass % of the urea-basedthickener, and 0.6 mass % to 3.6 mass % of the sodium soap thickener,based on the total amount of the grease composition, as shown in Table5, the average Anderon value is less than 15 and the acousticperformance is good in any of the above heat resistance test and loadresistance test.

On the other hand, as shown in Table 6, when only one type of thickeneris contained (Comparative Example 1 to Comparative Example 10), theacoustic performance relating to the load resistance deteriorates whenonly fluorine-based thickener is contained (Comparative Example 1), andthe acoustic performance relating to the heat resistance deteriorateswhen only urea-based thickener (Comparative Example 2 to ComparativeExample 4) or only soap-based thickener (Comparative Example 5 toComparative Example 10) is contained.

In addition, when only a fluorine-based thickener and a urea-basedthickener are contained without a soap-based thickener (ComparativeExample 11 to Comparative Example 13), the heat resistance is good butthe acoustic performance relating to the load resistance deteriorates.

Further, when a fluorine-based thickener and a calcium complex soapthickener are contained without a urea-based thickener (ComparativeExample 14 to Comparative Example 16), a fluorine-based thickener and acalcium soap thickener are contained without a urea-based thickener(Comparative Example 19 to Comparative Example 21), a fluorine-basedthickener and a barium soap thickener are contained without a urea-basedthickener (Comparative Example 24 and Comparative Example 25), afluorine-based thickener and a magnesium soap thickener are containedwithout a urea-based thickener (Comparative Example 31 and ComparativeExample 32), or a fluorine-based thickener and a sodium soap thickenerare contained without a urea-based thickener (Comparative Example 38 andComparative Example 39), the load resistance is good but the acousticperformance relating to the heat resistance deteriorates (see Table 7and Table 8).

Furthermore, in the case where three types of thickeners, i.e., afluorine-based thickener, a urea-based thickener and a soap-basedthickener are contained, and when the blending amount of the calciumcomplex soap thickener is out of (larger than) the range specified bythe embodiment of the present invention (Comparative Example 17 andComparative Example 18), the blending amount of the calcium soapthickener is too large (Comparative Example 22 and Comparative Example23), the blending amount of the barium soap thickener is too large(Comparative Example 29 and Comparative Example 30), the blending amountof the magnesium soap thickener is too large (Comparative Example 36 andComparative Example 37), or the blending amount of the sodium soapthickener is too large (Comparative Example 43 and Comparative Example44), the load resistance is good, but the acoustic performance relatingto the heat resistance deteriorates. On the other hand, also in the casewhere three types of thickeners are contained, and when the blendingamount of the barium soap thickener is out of (smaller than) thespecified range specified by the present invention (Comparative Example26 to Comparative Example 28), the blending amount of the magnesium soapthickener is too small (Comparative Example 33 to Comparative Example35), or the blending amount of the sodium soap thickener is too small(Comparative Example 40 to Comparative Example 42), the heat resistanceis good, but the acoustic performance relating to the load resistancedeteriorates (see Table 7 and Table 8).

When a lithium soap thickener is used in combination as a soap-basedthickener (Comparative Example 45 to Comparative Example ComparativeExample 51), the acoustic performance relating to the load resistancedeteriorates. When the blending amount of the lithium soap thickener islarger than 1.3 mass %, the acoustic performance relating to the heatresistance also deteriorates (see Table 9 and FIG. 7).

As described above, it is confirmed that, the grease composition of thepresent invention, to which a fluorine-based thickener, a urea-basedthickener, and a soap-based thickener selected from the group consistingof a calcium complex soap thickener, a calcium soap thickener, a bariumsoap thickener, a magnesium soap thickener and a sodium soap thickenerare added, can prevent noise increase and have good heat resistance(high temperature high speed characteristic) and load resistance (highload characteristic) even in use under a high temperature environment(for example, 180° C. or higher) and under a high load condition (forexample, 500 N).

In Examples, the acoustic characteristic is evaluated using a standardsmall diameter ball bearing having an outer diameter of 22 mm. However,the rolling bearing to which the present disclosure is directed is notlimited to this size, and the size of the rolling bearing according tothe embodiment of the present disclosure can be suitably selected, andalso the type of the rolling bearing can be suitably selected.

Although the invention has been described with respect to specificembodiments for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

DESCRIPTION OF REFERENCE NUMERALS

-   G . . . Grease composition-   10 . . . Rolling bearing-   11 . . . Inner ring-   11 a . . . Raceway-   12 . . . Outer ring-   12 a . . . Raceway-   13 . . . Rolling element-   14 . . . Cage-   15 (15 a, 15 b) . . . Annular sealing member-   16 . . . Bearing space

1. A grease composition, comprising: a fluorine-based base oil and anon-fluorine-based base oil, as base oils; and a fluorine-basedthickener, a urea-based thickener and at least one soap-based thickenerselected from the group consisting of a calcium complex soap thickener,a calcium soap thickener, a barium soap thickener, a magnesium soapthickener and a sodium soap thickener, as thickeners, wherein the greasecomposition comprises: based on a total amount of the greasecomposition, 70 mass % to 90 mass % of a total amount of thefluorine-based base oil and the non-fluorine-based base oil; 9 mass % to18 mass % of the fluorine-based thickener; and 0.5 mass % to 7 mass % ofthe urea-based thickener.
 2. The grease composition according to claim1, wherein the urea-based thickener contains at least one of analiphatic-aromatic urea, an alicyclic-aliphatic urea and an aliphaticurea.
 3. The grease composition according to claim 2, wherein theurea-based thickener contains a diurea compound represented by thefollowing General Formula (1):R₁—NHCONH—R₂—NHCONH—R₃  (1) (in the formula, R₁ and R₃ eachindependently represent a monovalent aliphatic hydrocarbon group, amonovalent alicyclic hydrocarbon group or a monovalent aromatichydrocarbon group, and at least one of R₁ and R₃ represents a monovalentaliphatic hydrocarbon group or a monovalent alicyclic hydrocarbon group,and R₂ represents a divalent aromatic hydrocarbon group).
 4. The greasecomposition according to claim 1, comprising 0.3 mass % to 3 mass % ofthe calcium complex soap thickener based on the total amount of thegrease composition.
 5. The grease composition according to claim 4,wherein the calcium complex soap thickener is a calcium complex soap ofan aliphatic dicarboxylic acid and a monoamide monocarboxylic acid. 6.The grease composition according to claim 1, comprising 0.3 mass % to 3mass % of the calcium soap thickener based on the total amount of thegrease composition.
 7. The grease composition according to claim 1,comprising 0.6 mass % to 3.6 mass % of the barium soap thickener basedon the total amount of the grease composition.
 8. The grease compositionaccording to claim 1, comprising 0.6 mass % to 3.6 mass % of themagnesium soap thickener based on the total amount of the greasecomposition.
 9. The grease composition according to claim 1, comprising0.6 mass % to 3.6 mass % of the sodium soap thickener based on the totalamount of the grease composition.
 10. The grease composition accordingto claim 1, wherein the non-fluorine-based base oil is one or moreselected from the group consisting of a hydrocarbon-based synthetic oil,an ether-based synthetic oil, an ester-based synthetic oil, and asilicone-based synthetic oil.
 11. A rolling bearing which is filled withthe grease composition according to claim 1.